linux-kernel - Re: [PATCH v2 2/2] xen: events: free irqs in error condition

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Date:   Wed, 28 Feb 2018 08:16:23 +0000
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     "Shah, Amit" <aams@...zon.de>
CC:     "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "Valentin, Eduardo" <eduval@...126.com>,
        "jgross@...e.com" <jgross@...e.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "shuo.a.liu@...el.com" <shuo.a.liu@...el.com>,
        "anoob.soman@...rix.com" <anoob.soman@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH v2 2/2] xen: events: free irqs in error condition

On Tue, Feb 27, 2018 at 05:32:53PM +0000, Shah, Amit wrote:
> 
> On Di, 2018-02-27 at 17:07 +0000, Roger Pau Monné wrote:
> > On Tue, Feb 27, 2018 at 03:55:58PM +0000, Amit Shah wrote:
> > > 
> > > In case of errors in irq setup for MSI, free up the allocated irqs.
> > > 
> > > Fixes: 4892c9b4ada9f9 ("xen: add support for MSI message groups")
> > > Reported-by: Hooman Mirhadi <mirhadih@...zon.com>
> > > CC: <stable@...r.kernel.org>
> > > CC: Roger Pau Monné <roger.pau@...rix.com>
> > > CC: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > > CC: Eduardo Valentin <eduval@...zon.com>
> > > CC: Juergen Gross <jgross@...e.com>
> > > CC: Thomas Gleixner <tglx@...utronix.de>
> > > CC: "K. Y. Srinivasan" <kys@...rosoft.com>
> > > CC: Liu Shuo <shuo.a.liu@...el.com>
> > > CC: Anoob Soman <anoob.soman@...rix.com>
> > > Signed-off-by: Amit Shah <aams@...zon.com>
> > > ---
> > >  drivers/xen/events/events_base.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/xen/events/events_base.c
> > > b/drivers/xen/events/events_base.c
> > > index c86d10e..a299586 100644
> > > --- a/drivers/xen/events/events_base.c
> > > +++ b/drivers/xen/events/events_base.c
> > > @@ -750,11 +750,14 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev
> > > *dev, struct msi_desc *msidesc,
> > >  
> > >  	ret = irq_set_msi_desc(irq, msidesc);
> > >  	if (ret < 0)
> > > -		goto error_irq;
> > > +		goto error_desc;
> > >  out:
> > >  	mutex_unlock(&irq_mapping_update_lock);
> > >  	return irq;
> > >  error_irq:
> > > +	while (--nvec >= i)
> > > +		xen_free_irq(irq + nvec);
> > > +error_desc:
> > >  	while (i > 0) {
> > >  		i--;
> > >  		__unbind_from_irq(irq + i);
> > It seems pointless to introduce another label and another loop to fix
> > something that can be fixed with a single label and a single loop,
> > this just makes the code more complex for no reason.
> 
> I disagree, just because there are two different cleanups to be made
> for two different issues; it's not as if the if.. and else conditions
> are going to be interleaved.

Oh, I don't mind so much whether it ends up being two patches or a
single one, but IMHO the code should end up looking similar to what I
proposed, I would like to avoid having two loops and two labels.

Could you rework the series so that the end result uses a single loop
(and label)?

Thanks, Roger.